1. Field of the Invention
The present invention relates to a coupling apparatus for attaching a working implement to the front of a tractor.
2. Description of the Related Art
Numerous improvements have been made heretofore in relation to the working implement coupling structure to facilitate attachment and detachment of working implements to/from tractors. One example of such improvements is described in U.S. Pat. No. 4,936,737. According to this working implement coupling apparatus, a pair of right and left masts pivotally support proximal ends of booms, and a bucket is attached to distal ends of the booms to act as a working tool. The apparatus includes boom cylinders for adjusting angles of the booms relative to the masts.
The masts are attached to mast mounts formed on a tractor body to be pivotable about a pivotal axis. A pair of fight and left braces extend forwardly and downwardly from the respective masts. The braces have forward ends thereof interconnected through a cross tube (or cross rod). The cross tube is attached to and detached from brace connectors arranged in front positions of the tractor body, by locking and unlocking a locking device.
For detaching the working implement in the above conventional structure, the locking device of the brace connectors is unlocked to release the cross tube (cross rod) from a front support assembly (corresponding to the brace connectors). Then, the boom cylinders are extended to swing the masts forward relative to the mast mounts. As a result, the forward ends of the braces are lowered to the ground. With the braces and working tool (bucket) resting on the ground, the masts are drawn upward from the mast mounts.
According to the above working implement coupling apparatus, however, the boom cylinders must be extended through a long stroke before the forward ends of the braces contact the ground. This leaves room for improvement in that a working implement detaching operation is a slow process.